Hey guys, been traveling a lot lately and it's good to come back to The 6! Best of all, I finally drove my car today for the first time in a month! Cooler weather is here and the car feels GREAT, but here is my issue. My wastegates are probably dialed in too tight. I consistently see 18-20psi (1.2-1.3 bar) in all gears to redline, with spikes as high as 25psi (1.7 bar) between gears. This happened last time at the track as well. My AFRs are between 11.3-11.6 to redline which seems pretty safe to me.

I've adjusted my BOV all I can, and have reached the conclusion that either I have to dial back my wastegates (although the initial boost pressure is ok, I don't see how that would help with my between-shift spikes ), or a single adjustable BOV simply cannot relieve all of the boost pressure adequately.

Questions:
- can the motor take this kind of boost ok on GIAC street file with 98 octane fuel (102RON => 98 US) and the AFRs that I'm showing?
- has anyone else who has gone to a single BOV setup seen this kind of behavior (spikes)?

For now I've adjusted my BOV to not hold as much pressure, but I'm still seeing the between shift spikes. Obviously having the excess boost vent this way is not the best solution. Thanks for your help fellas, hoping to get this sorted before the track tomorrow (temps in the upper-40's mmmmmmmm!)

Later

 

jimmer - i was also seeing the same spikes. The only thing between your turbos and your engine is the BOV, and if its too stiff its not doing its job.

I took it out, unscrewed it until there was no pressure felt then I did 2 turns. Under normal driving it blows off at .4 bar and above(I think it could be tighter). I was really worried seeing spikes because its putting so much pressure on the impellers between shifts. Not only is it your turbos at risk but I would think your combustion chamber doesnt like 1.7 bar and no fuel being pumped it to it - JIMO.

 

Yeah, I unscrewed it but now it's just not holding boost well and boost is decreasing as rpms rise. Now that I think about it, the spikes between shifts isn't a real worry I guess because we have the benefit of a shut throttle plate which keeps that boost from reaching the engine - the boost is being measured before this. A lot of turbo cars don't even have BOVs, and you hear that flutter sound when shifting. You're right, it's still no good for the turbos though.

I think I'm going to tighten it back up to hold the 18-20psi, and as long as my AFRs look ok then all should be good. Still think that the single BOV isn't venting enough (it's the only thing that could be causing the spikes), and will prolly go back to a 2 valve solution over the winter to save the turbos, although I sure will miss that sound...

 

Jim, You will have to dial them back here for sure, our weather get's well cool and if you are on the edge at the moment, you will be over it over the next few months!

I have to do it every year.

Did u get me address?

 

jimmer you might be right. Did Dan tell you it was better than the 2 dv's also? It sounded good at first but now I feel like I wasted a few hundred bucks...

 

boost controller time lol


S

 

Jimmer,
dial it down a bit.

When is your standing mile run??? I am getting thirsty for some good beer! LOL!

good luck,

Marty

 

Hey Marty, yes sir. I was going to dial it back this weekend, but it rained the whole time so I didn't even want to get it ready for the track. Now that I finally have a proper jack, I'll crawl under there this week to see what's up.

I guess my original question may have been misunderstood. Given good fuel and A/F ratios, what's the max boost the stock motors have been known to be able to take? 1.7 bar? More?

VMAX Glacier is Nov 11th. Should have the new intercoolers and pipes on, as well as some porting. It will be close...

 

my tuner is not in favore of the single unit BOV. this should not be happening.
we had a single bov on a car and it was doing funcky stuff.

btw, how are u getting mid 11s afrs. Giac tunes for low 12s like it should be.

 

Depends on the turbos....your stock k16's are probably done at anything past 1.0 bar and would only be blowing hot air.......a gt28 or other aftermarket turbo stay away from anything over 1.5 bar with the stock head gaskets and head studs.

 

Yeah, I'm going to ditch it over the winter, thanks Mark. What are you running, two BOV custom-plumbed right after each IC outlet? I'm looking for creative ideas for a project over the winter. I was thinking of going back to a 2 BOV system but putting one on each side rather than in parallel.

I don't know about my AFR's. I watched them in 3rd and 4th gear pulls the other day and they're at 11.1-11.4 as long as I was watching @ about 19lbs boost. It's the AEM gauge, so it should be pretty accurate. I'm working with Stephen so maybe he built some additional cushion into the programming knowing my propensity for turning up the boost.

 

Thanks Joe

 

Running so rich actually rob's u of power.
I think u have upgraded Wgs... but with K16s there is not much u can do.
just get some forged dvs and try that.... you want them to recirculate anyways... changing the position of ur dvs is useless unless ur going wiith bigger ICs...but then wiht K16s its pointless.

 

Oh, but I do my friend. My shiny new EVOM ICs are sitting right here in front of me. Always thinking about the future course of the car you know...

 

Great Thread.......